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TPS281C30: Current sensing capabilities

Amir Alipour
Prodigy 20 points
Part Number: TPS281C30
Other Parts Discussed in Thread: TPS2H000-Q1

Tool/software:

Hi there,
I'm driving an inductive load with 24V PWM signals with 150HZ.

The range of load current that is important to us is between 200-800mA.
What is the most accurate result that I can get out of the device if I'm driving the EN and DIAG_EN pins with 3V3.
Can I count on measuring with  1mA accuracy? What about 10mA?
It seems that at least in data sheet 10% accuracy. meaning that for 200mA, I will get +_20mA accuracy?
And this is with V_DIAG = 5 (might be worse with 3V3 ?) and also there is a tsns that is comparable to 150HZ (Is that going to make some problems as well?

Kind Regards,

  • 0
    TI__Mastermind 29480 points

    Hi Amir,

    That is correct, at 200mA, you will have 10% or +/-20mA accuracy over temp. At 800mA, you will have 6% accuracy, or +-48mA. In reality at 800mA, the accuracy will be closer to 5%/40mA max, but 6% should be designed around as it is in the data sheet.

    V_DIAG_EN = 5V and 3.3V will be the same. As per the data sheet, the settling time for current sense is 20us max so this is negligible compared to 150Hz.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Prodigy 20 points

    Patrick,
    Thanks for your response.

    Taking these into account, what is your suggestion for 1mA accuracy?
    Do you have any Switch with 1.5KHZ max freq and max current=4A with a current measurement circuitry capable of 1mA accuracy?
    If not a compact solution, A shunt resistor on the Vs and Amplifier then (high side current Op Amp)? Any suggestion for the Op Amp in Ti portfolio?

  • 0 in reply to Amir Alipour
    TI__Mastermind 29480 points

    Hi Amir,

    1mA accuracy at 200mA+ is very hard to achieve. The closest integrated solution would be TPS2H000-Q1, which can achieve 5mA accuracy at 200mA, or 20mA accuracy at 800mA.

    1.5kHz is achievable with any of the switches if the turn on/off delay times and slew rates work in your application. Those parameters define what proportion of the time the output voltage is VS vs GND.

    I'll loop in the current sense amplifier team to make a recommendation on a current sense amp device.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    TI__Mastermind 34260 points

    Hi Amir,

    Some of our high accuracy current sense amplifiers can meet the requirement in terms of gain error (<0. 1%). You can take a look at the INA241 for example.

    Offset is likely going to be the next limiting factor. In the end you may need to choose a larger Rshunt value, and still calibration may be necessary.

    Regards

    Guang